1. Field of the Invention
The present invention relates to apparatus for changing the rolls of a skew rolling mill.
2. Description of the Prior Art
In a skew rolling mill tapered rolls are arranged overhung on the end of a respective shaft on which they are detachably mounted. The shafts of the tapered rolls are inclined with respect to the axis of the material to be rolled and pass that axis at a short distance therefrom, resulting in an inclination of the tapered rolls which effects the advance of the material to be rolled. The inclination to be selected is determined by the diameter, the quality of material and the surface finish of the product to be rolled, so that in the case of a skew rolling mill provided solely for uniform application setting, means for altering the inclination may be dispensed with. Otherwise the shafts of the tapered rolls are mounted in roll heads which are pivotable about axes parallel to the axis of the material to be rolled in a roll carrier or rotor of the rolling mill in order to allow the inclination of the tapered rolls to be set. In addition, the shafts of the tapered rolls are axially adjustable in order to allow the size or the external size of the material to be rolled (solid or hollow section) to be set.
Changing the tapered rolls by means of tongs, which are suspended from a crane and grip one tapered roll in turn, is very time-consuming. For this reason changing devices are used which are provided on a carrier with a number of roll clamping devices which corresponds to the number of rolls (three). The carrier with the clamping devices is arranged on a changing carriage. The carrier is displaceable upon the said changing carriage in the direction of the axis of the material to be rolled in order to be able to bring the clamping devices to the tapered rolls. The carrier may be moved with the changing carriage transversely to the axis of the material to be rolled in order to allow the changing apparatus to be moved out of the rolling axis. In order to speed up the roll change further, the changing carriage is provided with two carriers which are pivotable about an axis arranged transverse to the axis of the material to be rolled in the manner of a revolver, so that one carrier can grip the tapered rolls to be dismounted with its clamping devices, while the other carrier holds the tapered rolls to be newly inserted with its clamping devices and conveys them (after rotation of the two carriers) to the shafts (see for example German Offenlegungsschrift No. 28 23 139).
Despite the use of the changing carriage described above, the roll change cannot be carried out in as short a time as desired, since it has been found to be difficult and time-consuming to move the clamping devices with their carriers into the position required for the roll change sufficiently precisely by means of the changing carriage and to hold them in this position.